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https://issues.apache.org/jira/browse/CALCITE-4154?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17171732#comment-17171732
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Julian Hyde edited comment on CALCITE-4154 at 8/5/20, 8:16 PM:
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[~amaliujia], Optimizations other than projection are possible. For example,
{{COALESCE(SUM\(x), 0)}} can be converted to {{SUM0\(x)}}. (To see why {{SUM0}}
is superior, see CALCITE-3957.)
was (Author: julianhyde):
[~amaliujia], Optimizations other than projection are possible. For example,
{{COALESCE(SUM(x), 0)}} can be converted to {{SUM0(x)}}. (To see why {{SUM0}}
is superior, see CALCITE-3957.)
> Add a rule to merge a Project onto an Aggregate
> -----------------------------------------------
>
> Key: CALCITE-4154
> URL: https://issues.apache.org/jira/browse/CALCITE-4154
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Add a rule to merge a {{Project}} onto an {{Aggregate}}. In practice, it
> means that aggregate functions that are not used in the Project are removed
> from the Aggregate.
> For example,
> {code:java}
> SELECT deptno, sum_sal
> FROM (
> SELECT deptno, job, SUM(sal) AS sum_sal, MIN(ename) AS min_ename
> FROM emp
> GROUP BY deptno, job)
> {code}
> becomes
> {code:java}
> SELECT deptno, sum_sal
> FROM (
> SELECT deptno, job, SUM(sal) AS sum_sal
> FROM emp
> GROUP BY deptno, job)
> {code}
> Note that {{min_ename}} is removed from the {{Aggregate}} (because it is not
> used by the {{Project}}). {{job}} is not used, but it remains because it is a
> {{GROUP BY}} key.
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